Method and apparatus for automated filling of a mail tray from a vertical stacker

ABSTRACT

An automated mail tray filling apparatus for taking envelopes from a vertical stacker output of an inserter machine and placing them in mail trays. A vertical stack of envelopes rests on a long stacker table. The mail tray filling apparatus has a track positioned next the vertical stacker table parallel to the length of the vertical stacker table. A mail tray transport is positioned beneath the track and arranged to transport mail trays beneath the track in a direction parallel to the vertical stacker table. A movable mail tray filler is movably mounted on the track to travel in parallel next to the vertical stacker table and above the mail tray transport, and is arranged to withdraw envelopes from the end of the vertical stack in a sideways direction. Envelopes are then redirected into a downward direction and fed into a mail tray positioned beneath the movable mail tray filler.

TECHNICAL FIELD

The present invention relates to automated filling of mail trays withenvelopes from a mail production machine.

BACKGROUND OF THE INVENTION

A mail insertion system or a “mailpiece inserter” is commonly employedfor producing mailpieces intended for mass mail communications. Suchmailpiece inserters are typically used by organizations such as banks,insurance companies and utility companies for producing a large volumeof specific mail communications where the contents of each mailpiece aredirected to a particular addressee. Also, other organizations, such asdirect mailers, use mailpiece inserters for producing mass mailingswhere the contents of each mailpiece are substantially identical withrespect to each addressee.

In many respects, a typical inserter resembles a manufacturing assemblyline. Sheets and other raw materials (i.e., a web of paper stock,enclosures, and envelopes) enter the inserter system as inputs. Variousmodules or workstations in the inserter system work cooperatively toprocess the sheets until a finished mail piece is produced. The preciseconfiguration of each inserter system depends upon the needs of eachcustomer or installation.

Typically, inserter systems prepare mall pieces by arranging preprintedsheets of material into a collation, i.e., the content material of themail piece, on a transport deck. The collation of preprinted sheets maycontinue to a chassis module where additional sheets or inserts may beadded based upon predefined criteria, e.g., an insert being sent toaddressees in a particular geographic region. From the chassis modulethe fully developed collation may continue to a stitched module wherethe sheet material may be stitched, stapled or otherwise bound.Subsequently, the bound collation is typically folded and placed intoenvelopes. Once filled, the envelopes are closed, sealed, weighed, andsorted. A postage meter may then be used to apply postage indicia basedupon the weight and/or size of the mail piece. The mailpieces will thenbe moved to a stacker where mailpieces are collected and stacked, eitheron edge or laid flat. An exemplary on-edge stacker, or vertical stacker,is depicted in U.S. Pat. No. 6,398,204 titled On-Edge StackingApparatus, which is hereby incorporated by reference in its entirety.

In a final step, the mailpieces are manually removed by an operator fromthe stacker and placed into mail trays or other storage containers. Suchmanual collection and removal is pragmatic, reliable and fiscallyadvantageous when the time of mailpiece removal can be shared and/orabsorbed within the overall labor requirements associated withmanaging/operating the mailpiece inserter system. That is, this task canbe efficiently performed when sufficient idle time exists betweenvarious other operational tasks, e.g., removing out-sorted mailpieces,cleaning/removing paper dust from various optical readers/scanningdevices, etc., to periodically or intermittently unload the mailpiecestacker.

Advances in the art of mailpiece inserters have vastly increased thetotal mailpiece volume and rate of mailpiece production. For example,the Advanced Productivity System (APS) inserter system produced byPitney Bowes Inc., located in Stamford, Conn., USA, can produce as manyas twenty-six thousand (26,000) mailpieces in one hour of operation.Accordingly, hundreds of mail trays, collectively weighing over 11,000lbs, must be removed and transported each hour by a system operator. Infact, the volume of mailpieces produced is sufficiently large thatseveral system operators may be required to concentrate on thesingle/sole task of mailpiece collection and removal. Aside from thetime associated with this final unloading step, it will be appreciatedthat the collection, removal and transport of such large mailpiecequantities can be highly demanding in terms of the physical workload. Itwill also be recognized that such physical demands can lead toinconsistent or reduced mailpiece throughput if/when the workloadrequirements are not properly balanced with the high volume mailpieceoutput.

A need, therefore, exists for an apparatus for stacking mailpiecesproduced by high volume mailpiece inserters, which apparatus ensuresconsistent throughput, is fiscally advantageous and provides a viablealternative to manual mailpiece collection and removal.

Prior art systems that have attempted to meet this need include: (i) adevice that lifts mail trays onto their side to receive pre-formedstacks of envelopes (U.S. Pat. No. 7,600,751); (ii) a stationary devicethat individually fed envelopes into a mail tray that had been lifted upfrom below (U.S. Pat. No. 6,536,191); and (iii) a device that droppedvertical stacks of envelopes into mail trays using a trap-doorarrangement (U.S. Pat. No. 5,347,790).

SUMMARY OF THE INVENTION

The invention is an automated mail tray filling apparatus for takingenvelopes from a vertical stacker output of an inserter machine andplacing them in mail trays. The vertical stacker provides a verticalstack of finished envelopes on a long vertical stacker table. Thevertical stacker table is capable of transporting the vertical stackaway from an inserter output where envelopes are added to the stack.

The mail tray filling apparatus described herein can easily be combinedwith an existing vertical belt stacker such as the one described in U.S.Pat. No. 6,398,204, On-Edge Stacking Apparatus, incorporated byreference herein. Minimal modifications are needed to an existinginserter and vertical stacker to enable them to work in combination withthe new tray filler apparatus.

In a preferred embodiment, the existing vertical stacker operates in itsnormal fashion. The tray filling apparatus includes independentintelligence that senses the presence of stacked envelopes and feeds theenvelopes into waiting trays. A movable mail tray filler is capable ofmoving back and forth relative to the length of the vertical stack, sothat the stacker can continue to feed regardless of variations in theoutput from the inserter machine to the vertical stacker.

In this fashion, the vertical stacker acts as a buffer for the trayfilling apparatus. Even if there is an interruption in the production offilled envelopes from the inserter machine, the tray filling apparatuscan continue feeding by moving the feeding component along the stacktowards its upstream end. If the tray filling apparatus needs to pause,to change mail trays, for example, then the movable tray filler can movedownstream on the vertical stacker to allow space for more envelopes tobe added from the inserter.

The mail tray filling apparatus has a track positioned next the verticalstacker table parallel to the length of the vertical stacker table. Amail tray transport is positioned beneath the track and arranged totransport mail trays beneath the track in a direction parallel to thevertical stacker table. A movable mail tray filler is movably mounted onthe track to travel in parallel next to the vertical stacker table andabove the mail tray transport and arranged to withdraw envelopes from adistal end of the vertical stack in a sideways direction. Envelopes arethen redirected into a downward direction and fed into a mail traypositioned beneath the movable mail tray filler.

A take-away feeder is positioned over the vertical stacker table andarranged to withdraw individual envelopes from the vertical stack in asideways direction. The take-away feeder includes a pressure sensor todetermine if there is enough pressure to feed envelopes from the stack.

The movable mail tray filler can move back and forth along the track inresponse to different pressure conditions at the pressure sensor. Thefiller transport moves incrementally on the track towards the inserteroutput end of the vertical stacker when the vertical stack pressure isless than a predetermined threshold, thereby moving the take-away feederinto closer contact with the distal end of the vertical stack. When themail tray filler is in a non-feeding mode, the take-away feeder isallowed to move down the stacker to make room for additional envelopes.

After the envelope has been removed in the sideways direction, theenvelope is redirected in a downward direction by first ejecting theenvelope into an open space. A downward tamping mechanism positionedabove the open space moves downward to push on a top edge of thefree-floating envelope. A downward transport positioned beneath the openspace receives and transports envelopes pushed downward by the downwardtamping mechanism.

Preferably, the downward tamping mechanism is an inverted L shapedpusher, positioned to contact the top edge of the envelope on aninterior corner of the inverted L. In the preferred embodiment thedownward motion of the pusher is at an acute angle to push the envelopetowards the receiving transport.

Feeding of envelopes from the vertical stacker into the mail tray filleris preferably controlled so as to maintain a stack size that is withinan optimal range. Stacks that are too short may not have consistentpressure at the take-away feeder. Stacks that are too long may result inskewed stacks because of uneven thickness of the mail in the envelopes.Allowing very long vertical stacks could also require additionalmachinery and structure to handle mail trays that need to be positionedunderneath the filler apparatus. Such additional structure could have anegative impact on the desired floors space footprint of the apparatus.

To achieve feeding within the optimal range on the vertical stacker, themail tray filler apparatus operates as a function of the pressuredetected at the take-away feeder, the position of the take-away feeder,and the operational status of the mail tray filler. The apparatusdetermines whether a predetermined trigger pressure has been reached atthe pressure sensor. The apparatus also determines whether the mail trayfiller is in a paused mode.

If the predetermined trigger pressure has been exceeded, and the mailtray filler is not in pause mode, then envelopes are fed from thevertical stack using the take-away feeder. If the predetermined triggerpressure has been exceeded, and the mail tray filler is in pause mode,then envelopes are not fed from the vertical stack and the mail trayfiller is moved in a downstream direction of the vertical stacker,thereby making room for more envelopes on the vertical stacker. If thepredetermined trigger pressure has not been exceeded, and the mail trayfiller is not in pause mode, then the mail tray filler is moved in anupstream direction of the vertical stacker to bring the take-away feederinto contact with the vertical stack. If the take-away feeder is notwithin the optimized range, the stack is allowed to get bigger until itis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the mail tray filler apparatus next to a vertical stackermodule in the preferred arrangement.

FIG. 2 shows the paper path for feeding envelopes from the stacker intomail trays.

FIG. 3 is a top view of mechanism for feeding envelopes from thevertical stacker in the sideways direction.

FIG. 4 is an isometric view showing an envelope being fed from thevertical stack.

FIG. 5 is a side view of the mail tray filler showing the downwardenvelope path.

FIG. 6 is an isometric view showing an envelope that is undergoing aright angle turn in accordance with the preferred embodiment.

FIG. 7 is an isometric view showing an envelope as it is being depositedat the end of a stack of envelopes in a mail tray.

FIG. 8 is a flow diagram for controlling feeding and positioning of themail tray filler and take-away feeder relative to the vertical stacker.

FIG. 9 is a flow diagram showing the operation of the arrangement forfeeding envelopes downward into the mail tray.

FIG. 10 is a flow diagram showing an operation for repacking envelopesalready placed in a partially full tray.

FIG. 11 is a flow diagram for an alternative mode of operating thearrangement for feeding envelopes downward into the mail tray.

DETAILED DESCRIPTION

FIG. 1 shows the arrangement of the mail tray filler apparatus 4relative a conventional vertical stacker unit 1 typically used at theoutput end of a high speed mail inserter machine. The vertical stacker 1includes a horizontal table over which a flexible flat belt 2 ispositioned for the purpose of moving the vertical stack from an upstreamend of the table to a downstream end, as more envelopes from theinserter are added to the stack. A movable mail tray filler unit 6 ismovably mounted on tracks 5, enabling the mail tray filler 6 to move inthe upstream and downstream directions parallel with the verticalstacker 1.

The apparatus 4 is controlled using standard processors, controllers,and motors as used in the mail handling equipment field. In an exemplaryembodiment, the controller is a Mitsubishi Q series PLC (programmablelogic controller). A PLC is a specialized small computer with a built-inoperating system designed specifically for controlling machinery. PLCoperating systems are able to process incoming events and to react inreal time. Another advantage of a PLC is that it is designed to operatereliably in an industrial environment.

The PLC has input lines where sensors are connected to notify uponevents (e.g. pressures above/below a certain level, envelopes sensed ata particular location, etc.), and it has output lines to signal anyreaction to the incoming events (e.g. feed an envelope, move the mailtray. etc.). Where the system includes analog sensors (for exampleanalog pressure sensors) an A/D converter is used to generate thedigital signal for input into the PLC. The system is user programmableusing standard PLC programming language. Ladder logic programming isused in the preferred embodiment for programming the PLC for thefunctionality described herein.

In an alternative embodiment, control of the mail tray filler apparatus4 may be handled by a standard personal computer (PC), as are often usedin connection with operating systems for inserter systems. Thus, acontroller for the inserter system (and vertical stacker 1) may beconfigured to perform the same functions as the PLC. An advantage ofintegration with the inserter controller computer would be greatervisibility and tracking of mail pieces through the final processing andplacement in the mail trays.

The trayer apparatus 4 includes a touch screen display coupled to thecontroller to enable all of the interactions and inputs describedherein. For example, the display can show the operational status of themachine, and can be used for displaying or inputting various parametersfor machine operation, as described further herein. Any other type ofhuman-machine interface can also be used in place of a touch screendisplay.

For instances, where communication is desired between the trayerapparatus 4 and the vertical stacker 1 (and the corresponding insertersystem), a serial communication card may be used for communicationbetween the respective controllers. In the preferred embodiment thecontroller for the trayer apparatus 4 is an RS232 serial controller.

The movable filler unit 6 includes a take-away feeder 3 that istypically positioned at a downstream end of the envelope stack restingon the vertical stacker 1. The take-away feeder 3 serves as a support tohold the downstream end of the envelope stack upright, and movesupstream and downstream with the movable filler unit 6 to apply theappropriate pressure to maintain the stack of envelopes standingon-edge. A pressure sensor 9 is mounted on take-away feeder 3 forpurposes of detecting the stack pressure in connection with controllingfeeding operations and movement.

Beneath the movable filler unit 6 and tracks 5, a mail tray transport 7is positioned to provide mail trays 10 to be filled underneath movablefiller unit 6. In the preferred embodiment, mail trays 10 are moved intoposition for filling in a transport path parallel to the verticalstacker 1. Pushers 8 push the mail trays 10 on transport 7, and definethe relative positioning subsequent trays.

FIGS. 2-4 show the transport path by which the envelopes E move from thevertical stacker 1 into tray 10. A vacuum belt 11 on take-away feeder 3singulates envelopes from the stack in cooperation with a stripping unit23 and feeds them to transport nips 12. For this portion of theapparatus, it will be understood that other conventional mechanisms forseparating, feeding and transporting a vertical envelopes can be used.An optical sensor 22 positioned proximal to the take-away feeder 3detects the feeding of individual envelopes E from the stack.

Downstream of the nips 12 is the region of the filler unit 4 in whichthe envelope E is redirected in the downward direction. Preferably, thenips 12 feed the envelope into an open space. At the far end of the openspace is a stopping barrier 32. Above the open space is a downwardtamping mechanism 25 that serves to bat the envelope in a downwarddirection into downward feeding arm 20. In the preferred embodiment,downward feeding arm 20 is comprised of belts 27 and 28 that bringenvelopes to the feeding head 30 that deposits envelopes in a pack inthe tray 10.

The side view of FIG. 5 shows further details of the downward tampingmechanism 25 and the feeding arm 20. As discussed above, an envelope isejected from nips 12 so that it is free in open space beneath thedownward tamping mechanism 25 and above the belts 27 and 28 of thefeeder arm 20. The downward tamping mechanism 25 is activated by thedetection of a envelope being fed into the open space by an opticalsensor 22.

The downward tamping mechanism 25 may include an inverted L shapedpusher 21 that imparts a downward impact on the free floating envelope.Tamping mechanism 25 preferably includes an actuator configured to movethe pusher 21 up and down. The top of the pusher 21 pushes on the topedge of the envelope, while the vertical portion of the pusher 21applies a steadying force on a face of the envelope.

In the preferred embodiment, the downward tamping mechanism is arrangedso as to move at an angle that is not quite vertical. It has been foundthat moving the pusher 21 at an angle of ten degrees from verticalimparts both a vertical and horizontal force that causes the envelope tobe reliably pushed into the opening in transport belts 27 and 28 below.

As seen in FIG. 5, belts 27 and 28 spread apart from each other in theirupper reaches to facilitate the receipt of downward moving envelopes.Then the belts 27, 28 come together to form a typical belt transport formoving the envelope to the feeding head 30 that holds the pack ofenvelopes in the tray upright, and is angled so as to create a space forsubsequent envelopes to be added to the pack.

Feeding head 30 includes a tray pressure sensor 52 used for detecting apressure of the envelope pack in the tray 10 on the feeding head 30.Tray pressure sensor 52 may be a spring biased switch that is activatedwhen a particular pressure is applied. Alternatively, the pressuresensor can be of a strain gauge variety that is capable of providingcontinuous measurements of the force being applied to the feed arm 20.

On a rear region of the feed arm 20 an end-of-tray sensor 50 can bemounted on the feed arm support structure 51. The end-of-tray sensor 50may be a mechanical switch that is activated when it comes into contactwith a rear wall of tray 10. Alternately, sensor 50 could be replacedwith an optical sensor, or other type of proximity sensor, to achieve asimilar result. An envelope sensor 22 is positioned proximal to thebelts 27 and 28 to detect envelopes transported in the feeding arm 20.

Since the feeding arm 20 must be positioned within the tray 10 forfeeding, it is necessary that it be lifted out when it is time to removea completed tray and allow an empty tray to be positioned by the mailtray transport 7. For this reason the entire structure feeding arm 20 ismounted so as to be raised above the level of trays.

FIG. 6 shows an envelope E that has been ejected into the open spacebeneath the pusher 21. FIG. 7 shows the operation of feeding head 30 andbelts 27, 28 in feeding an envelope E into the mail tray pack.

FIG. 8 shows a preferred implementation for controlling the position ofthe take-away feeder 3 along the length of the vertical stacker 1. Ithas been found that if the take-away feeder 3 is too close to theupstream end of the vertical stacker 1 then the stack pressure can beinconsistent for optimal feeding. Also, by running the feeder 3 so closeto the input to the stacker 1 the benefits of using the stacker 1 as abuffer are lost.

If a stack gets too long on the stacker 1 then the shape of the stackcan be affected by thickness variations in the uniformity of envelopethicknesses. For example, envelopes being thicker on one side than theother can cause a stack to form a curve. Another issue with operatingthe feeder 3 towards the end of the stacker 1 is that such anarrangement will require additional structure for supporting andtransporting the trays on the tray transport 7. It may be more desirableto set a maximum length of the stack for feeding operations, rather thanadd extra floor-space footprint to the apparatus.

For these reasons, it has been found that the apparatus works best whenfeeding is maintained within an optimal range between a minimum andmaximum stack length. When there are no envelopes on the stacker 1, thetake-away feeder 1 does not start feeding until the stack length iswithin the optimal range. In the preferred embodiment, the stack isallowed to grow until it extends all the way to the maximum end of theoptimal length. Then, as feeding progresses, the movable tray filler 6and feeder 3 may gradually move closer to the upstream end of thestacker 1. If the feeder 3 gets closer than the minimum distance, thenthe feeder 3 stops, and the stack is allowed to grow again back to themaximum size in the optimal range. This range can be adjustable becausedifferent mail jobs will have different properties that may requiredifferent optimization.

The flow diagram of FIG. 8 shows the algorithm for the starting andmaintaining the position of the feeder 3 within the optimal range. Afterstarting the machine, with few or no envelopes accumulated in thestacker 1, the apparatus checks to see whether the stack is providingfeeding pressure on the take-away feeder (step 80). If trigger pressureis not detected at the sensor 9, then nothing happens and the systemwaits for more envelopes. If trigger pressure is detected, thenadditional logic is applied. At step 81 the system checks to see whetherthe feeder is paused. For example, if a mail tray is being changed thenenvelopes are not fed from the stack. If the feeder is paused, then,rather than feeding, the feeder 3 is moved incrementally downstream tomake room for more envelopes (step 82). The trigger pressure isadjustable for different mail jobs with envelopes having differentproperties, and the trigger pressure should be selected for optimalfeeding by the vacuum belt 11.

If the feeder is not paused, the system checks the position of thefeeder, which corresponds to the size of the stack (step 83). In theinitial startup scenario, the system wants the stack to grow to themaximum size in the optimal range, so until the stack size is equal to,or greater than, the maximum size, the feeder will keep movingincrementally downstream (step 82).

Once the feeder position has reached the optimal maximum position, thenfeeding of envelopes starts (step 84). Once feeding has started, thesensor 9 continues to check for the feeding trigger pressure (step 85).If no trigger pressure is detected, then the feeder 3 is movedincrementally upstream, towards the stack, so that feeding can continue(step 86). At step 87, when trigger pressure is detected, the systemagain consults the stacker position to determine whether the feeder hasmoved past the minimum optimal stacker length. If the position isgreater than the minimum, then feeding (step 84) continues. If the stacklength shrinks to less than the minimum, then the process for sendingthe feeder 3 downstream to the optimal maximum length starts again (step82, and 80, 81, 83).

In FIG. 9 a flow diagram shows the process for controlling the movementof the mechanism that places the envelopes into envelope packs in themail trays. At step 90, after an empty mail tray has been moved intoposition, the feeding arm 20 is lowered into the tray 10 so that feedhead 30 is in position to place the envelopes in their packed position.Then, envelopes are fed into the tray (step 91). During feeding, packpressure sensor 52 determines whether a maximum pack pressure is beingexceeded (step 92). If the pressure is being exceeded, then the frictionfor sliding a subsequent envelope into the pack may be too high, and thefeeder could jam. The predetermined threshold for the pack pressureshould be selected to maintain a firm vertical envelope stack at apressure less than pressure that would cause friction to preventsubsequent envelopes from sliding into the stack. Thus, to make moreroom when the pack pressure is high, the tray 10 is incremented forward(step 93). Moving the tray forward is done by moving the tray transportdownstream. Alternatively, this result could be achieved by moving thefeed arm 20, and movable mail filler 6, upstream.

Concurrently, the tray end sensor 50 can be triggered if the tray hasbeen moved along far enough to be almost full (step 94). Feeding resumeswhen the pack pressure sensor and the end of tray sensor are nottriggered (step 91). If the end of tray sensor is triggered, then thefeed arm 20 is lifted out of the tray (step 95) and an empty tray isadvanced (step 96).

Alternatively, to detecting the end of the tray using a sensor, thesystem can keep track of how many envelopes have been fed into a tray.Since the thickness of the envelopes, and the capacity of the trays canbe known in advance, the feed arm 20 removal and empty tray advancementsteps may be based on reaching a predetermined count of envelopes. Insome cases, there may be a particular need to fit a particular number ofenvelopes into a tray. In such cases, the pack pressure limits can beignored when the feeding head 30 approaches the rear of the tray, inorder that the desired quantity be filled.

FIG. 10 shows how an optional repack operation may be used in connectionwith the mail tray feeding. To fit more envelopes into a tray, it issometimes desirable to “repack” the envelopes one or more times duringfilling of the tray. Repacking is an operation that squeezes the pack topush the envelopes closer together. The reduction in the size of thepack after repacking can be the result of squeezing out excess air andredistributing pressure within the pack.

Repack operations are performed at predetermined intervals (step 100).Such interval could be based on a quantity of envelopes fed, or on thedistance the tray has moved during feeding. The number of repacks can beselected based on the importance of fitting a larger quantity ofenvelopes into a mail tray for a particular job. The repack interval mayalso be based on observation of a predetermined pressure profile beingsensed on the feeding arm from the stack of envelopes, for example ifthe pack pressure sensor 52 was a strain gauge that found the pressurewent below a predetermined threshold. If the predetermined interval hasbeen reached, then a repack operation is performed (step 101). In thepreferred embodiment, repacking is done by moving the mail traytransport 7 a predetermined distance in the upstream direct, thusforcing the envelope pack against the fed head 30. The repackingmovement may also be a function of moving the relative position of thefeed arm towards the front end of the mail tray until a predeterminedpressure is detected on the feed arm by a pressure sensor 52 straingauge. A similar result could be achieved by moving the feed arm 20downstream. When a repack interval is not in effect then the normalfeeding, pressure sensing and movement is in effect (steps 91, 102,103).

FIG. 11 shows an alternative technique for controlling the movementwhile feeding envelopes into the tray. Since the pack pressure can varyas envelopes conform to their space, and excess air escapes, the packpressure can increase and decrease during feeding. Thus, in addition toincrementing the mail tray forward to lessen the pack pressure, it mayalso be desirable move the mail tray backwards when the pack pressuredecreases. This idea is similar to doing the repack operation describedabove, but it is done on a more continuous basis. For this type ofmotion control, the pack pressure sensor 52 should preferably be of thestrain gauge variety so that force from the pack can be constantlymeasured.

Using this alternative technique, the system checks both whether thepack pressure is too high (step 105) or too low (step 106). If the packpressure is too high, then the tray is incremented forward (step 107),similar to the method shown in FIG. 9. However, if the pack pressure istoo low, then the tray is moved backward to bring the feed head intostronger contact with the pack (step 108). As discussed elsewhere thepressure settings for these steps is selectable to meet the particularproperties of different mail jobs.

FIG. 11, also includes an alternate method of detecting the end of atray. In this embodiment, the intended groupings of envelopes to beplaced in trays is predetermined. A mark is printed, or otherwise made,on the intended final envelope for a particular tray group. An opticalsensor, such as one of sensors 22, detects the end of tray marker on anenvelope, no more envelopes are fed from the vertical stacker 1 for thatparticular tray (step 109). The feeding arm is lifted out of the tray,and an empty tray is advanced (steps 95, 96).

As a supplement to the end-of-tray marking technique, it may still behelpful to count the quantity of envelopes being fed into a tray. Then,if the mark is not sensed, the system can stop feeding if the quantityexceeds a predetermined maximum. This prevents the trays fromoverfilling and causing the feeding mechanisms to jam.

Although the invention has been described with respect to preferredembodiments thereof, it will be understood by those skilled in the artthat the foregoing and various other changes, omissions and deviationsin the form and detail thereof may be made without departing from thespirit and scope of this invention.

What is claimed is:
 1. An automated mail tray filling apparatus fortaking envelopes from a vertical stacker output of an inserter machineand placing them in mail trays, the vertical stacker arranged to providea vertical stack of finished envelopes on a long vertical stacker table,the vertical stacker table being capable of transporting the verticalstack away from an inserter output where envelopes are added to thevertical stack; the apparatus comprising: a track positioned next thevertical stacker table parallel to the length of the vertical stackertable; a mail tray transport positioned beneath the track and arrangedto transport mail trays beneath the track in a direction parallel to thevertical stacker table; a movable mail tray filler movably mounted onthe track to travel in parallel next to the vertical stacker table andabove the mail tray transport and arranged to withdraw envelopes from adistal end of the vertical stack in a sideways direction, to redirectthe envelopes into a downward direction of travel, and feeding theenvelopes into a mail tray positioned beneath the movable mail trayfiller; wherein the movable mail tray filler comprises a take-awayfeeder positioned over the vertical stacker table and arranged towithdraw individual envelopes from the vertical stack into the movablemail tray filler in a sideways direction perpendicular to the directionof the stack; and wherein the take-away feeder includes a pressuresensor on the take-away feeder to determine a pressure of the verticalstack on the take away feeder, and whereby the pressure sensor iscoupled to a filler transport mechanism on the movable mail tray fillerto cause the movable mail tray filler to move along the track whenpredetermined pressure conditions are present.
 2. The apparatus of claim1 wherein the filler transport mechanism is configured to moveincrementally on the track towards the inserter output end of thevertical stacker when the vertical stack pressure is less than apredetermined threshold, thereby moving the take-away feeder into closercontact with the distal end of the vertical stack.
 3. The apparatus ofclaim 1 wherein the filler transport mechanism is configured to moveincrementally on the track away from the inserter output end of thevertical stacker when the vertical stack pressure is greater than apredetermined threshold, and the take-away feeder is in a non-feedingmode, thereby allowing the vertical stack to get longer.
 4. An automatedmail tray filling apparatus for taking envelopes from a vertical stackeroutput of an inserter machine and placing them in mail trays, thevertical stacker arranged to provide a vertical stack of finishedenvelopes on a long vertical stacker table, the vertical stacker tablebeing capable of transporting the vertical stack away from an inserteroutput where envelopes are added to the vertical stack; the apparatuscomprising: a track positioned next the vertical stacker table parallelto the length of the vertical stacker table; a mail tray transportpositioned beneath the track and arranged to transport mail traysbeneath the track in a direction parallel to the vertical stacker table;a movable mail tray filler movably mounted on the track to travel inparallel next to the vertical stacker table and above the mail traytransport and arranged to withdraw envelopes from a distal end of thevertical stack in a sideways direction, to redirect the envelopes into adownward direction of travel, and feeding the envelopes into a mail traypositioned beneath the movable mail tray filler; wherein the movablemail tray filler includes; a take-away feeder positioned over thevertical stacker table and arranged to withdraw individual envelopesfrom the vertical stack into the movable mail tray filler in a sidewaysdirection perpendicular to the direction of the stack; a downwardtamping mechanism downstream of the take-away feeder arranged to movedownward to impart a downward push on a top edge of an unsecuredfree-floating envelope that has been ejected from the take-away feeder;and a downward transport positioned beneath the downward tampingmechanism and positioned to receive and transport falling envelopespushed downward by the downward tamping mechanism.
 5. The apparatus ofclaim 4 wherein the downward tamping mechanism comprises an inverted Lshaped pusher.
 6. The apparatus of claim 5, wherein the inverted Lshaped pusher is positioned to contact the top edge of the envelope onan interior corner of the inverted L shaped pusher when the inverted Lshaped pusher is imparting the downward push.
 7. The apparatus of claim6, wherein the inverted L shaped pusher is arranged to push downwardtoward the envelope at an acute angle, whereby the pusher imparts forceson both the top edge and on a side of the envelope.